In the WiBro (Wireless Broadband Internet) which is a Korean wireless portable internet standard, the OFDM (Orthogonal Frequency Division Multiplexing) is used as a signal transmission scheme so as to provide the high speed data service in radio environment when a user moves. In addition, the OFDMA (Orthogonal Frequency Division Multiple Access) which is based on the OFDM is used as a multiple access scheme so that multi users might simultaneously receive the internet service.
Recently, to meet the increasing need for transmitting a large volume of data over wireless channels at high speed, intensive research is being conducted on multiple antennas technology using several antennas, and consequently, it is possible to transmit a large volume of data at high speed by combining beam forming technology, diversity technology, multiplexing technology (e.g. MIMO (Multiple Input Multiple Output) system), etc.
Among them, the MIMO system is a representative technology, which transmits data through multiple paths using multiple transmission antennas of a transmission side (e.g. base station) and multiple reception antennas of a reception side (e.g. terminal) so as to increase transmission capacity.
However, since not all terminals can support the MIMO system in present, terminals which can not support the MIMO system do not effectively use multiple transmission antennas of a base station.
In addition, in cases of transmitting preambles and/or broadcasting messages, it is difficult to apply the MIMO system regardless of whether a terminal can support the MIMO system or not. Thus, there is a demand for new schemes that can efficiently use multiple transmission antennas of a base station in these cases.